Field of the Invention
The present invention relates to a wire electric discharge machine having a function of cleaning a machining tank when the machining tank is contaminated with machining chips produced during electric discharge machining of a workpiece.
Description of the Related Art
A wire electric discharge machine applies voltage between a wire electrode and a workpiece disposed in a machining tank, thereby performing electric discharge machining of the workpiece. In this electric discharge machining, machining chips originating from the workpiece and the wire electrode are produced in each machining cycle. The machining chips are deposited on and contaminate a guide for applying the voltage to the wire electrode in the machining tank and a table on which the workpiece is set for the application of the voltage.
If the machining chips are left deposited on the guide and the table, they may cause improper voltage application between the wire electrode and the workpiece, so that it is important to clean the inside of the machining tank including the guide and the table.
Japanese Patent Application Laid-Open No. 2009-255223 discloses a technique in which abrasive particles and the like produced by water jet machining are removed from a machining tank by running water in a channel in the inner wall of the machining tank, in a multifunction machine for water jet machining and wire electric discharge machining.
In general, an operator cleans the inside of a machining tank after visually determining how machining chips are deposited in the machining tank, so that there may occur a reduction in the rate of operation of a machine and malfunction due to failure of cleaning. According to the technique disclosed in Japanese Patent Application Laid-Open No. 2009-255223 described above, it is impossible to automatically determine whether or not the inside of the machining tank is contaminated and clean the tank.